Board Thread:General Discussion/@comment-25235588-20171014004107/@comment-25235588-20171014024134

so just search gale forest for pikachu, and pikachu will turn into mimikyu. it wil say it's acting strange and it's mimikyu.
 * v0.15.1: 2017 Halloween Event begins. A special Pokémon can be found in Gale Forest overnight, while a dark portal may appear across one of the many places in Roria at night as well, leading the player to another special Pokémon. The event lasts until 31st October, 2017. (13/10/2017)

so far i think the best way to find that portal is to travel backwards starting from port deca and just folow the road from port deca to frostveil city DURING NIGHTTIME

both pokes can only be foun during nighttime